Sympathetic Neural Adaptation to Hypocaloric Diet With or Without Exercise Training in Obese Metabolic Syndrome Subjects

Abstract

OBJECTIVESympathetic nervous system (SNS) overactivity contributes to the pathogenesis and target organ complications of obesity. This study was conducted to examine the effects of lifestyle interventions (weight loss alone or together with exercise) on SNS function.RESEARCH DESIGN AND METHODSUntreated men and women (mean age 55 ± 1 year; BMI 32.3 ± 0.5 kg/m2) who fulfilled Adult Treatment Panel III metabolic syndrome criteria were randomly allocated to either dietary weight loss (WL, n = 20), dietary weight loss and moderate-intensity aerobic exercise (WL+EX, n = 20), or no treatment (control, n = 19). Whole-body norepinephrine kinetics, muscle sympathetic nerve activity by microneurography, baroreflex sensitivity, fitness (maximal oxygen consumption), metabolic, and anthropometric measurements were made at baseline and 12 weeks.RESULTSBody weight decreased by −7.1 ± 0.6 and −8.4 ± 1.0 kg in the WL and WL+EX groups, respectively (both P < 0.001). Fitness increased by 19 ± 4% (P < 0.001) in the WL+EX group only. Resting SNS activity decreased similarly in the WL and WL+EX groups: norepinephrine spillover by −96 ± 30 and −101 ± 34 ng/min (both P < 0.01) and muscle sympathetic nerve activity by −12 ± 6 and −19 ± 4 bursts/100 heart beats, respectively (both P < 0.01), but remained unchanged in control subjects. Blood pressure, baroreflex sensitivity, and metabolic parameters improved significantly and similarly in the two lifestyle intervention groups.CONCLUSIONSThe addition of moderate-intensity aerobic exercise training to a weight loss program does not confer additional benefits on resting SNS activity. This suggests that weight loss is the prime mover in sympathetic neural adaptation to a hypocaloric diet.

Different mechanisms in weight loss-induced blood pressure reduction between a calorie-restricted diet and exercise

“…In our previous study in obese Caucasian subjects with the metabolic syndrome, weight loss over 12 weeks with D+EX was associated with significantly greater decreases in total body fat mass, abdominal fat mass and waist-to-hip ratios than the D alone group, but reduction in plasma NE and NE spillover were greater in the D alone group compared with the combination group with D+EX. 52 The groups, including those in the EX program, had earlier and stronger improvements on HOMA-IR. 52 Taken together, a calorie restricted diet, but not aerobic exercise, is a prime mover in sympathetic nervous adaptation, and aerobic exercise may have a major role in the improvement of insulin resistance.…”

“…52 The groups, including those in the EX program, had earlier and stronger improvements on HOMA-IR. 52 Taken together, a calorie restricted diet, but not aerobic exercise, is a prime mover in sympathetic nervous adaptation, and aerobic exercise may have a major role in the improvement of insulin resistance. A calorie restricted diet and exercise may exert different mechanisms on weight loss, weight lossinduced BP reduction and insulin resistance.…”

“…54 In another study, comparing the effects of exercise and a calorie restricted diet on sympathetic nervous activity, the addition of moderateintensity aerobic exercise training to a weight-loss program did not confer additional benefits on resting sympathetic nervous activity as assessed from measures of whole-body NE spillover and muscle sympathetic nerve activity, although BP, baroreflex sensitivity and metabolic parameters improved significantly but similarly between the two study groups. 52 These studies demonstrated the importance of insulin resistance and the renin-angiotensin system for weight lossinduced BP reduction associated with aerobic exercise, however, these studies did not compare neurohormonal changes during the acute phase of weight loss. In the present study, at the early stage of weight loss, before significant weight loss at 8 weeks, suppression on plasma NE followed by a decrease in HOMA-IR and BP reduction was observed in the D alone group, whereas significant reduction in HOMA-IR followed by suppression on sympathetic nervous activity and BP reduction occurred in the EX alone group.…”

“…A number of investigations [17][18][19]52,53 have demonstrated the importance of exercise on weight loss and weight loss-induced BP reduction, however, few studies have examined the longitudinal differences in the mechanisms of weight loss between D alone and D+EX. Our recent study in obese Caucasian individuals with the metabolic syndrome demonstrated that exercise over 12 weeks had additional effects on weight loss and BP reduction and were associated with suppression of plasma renin activity compared with calorie restriction alone, whereas suppression of muscle sympathetic nervous activity was similar.…”

Cholesterol efflux from macrophages is influenced differentially by plasmas from overweight insulin-sensitive and -resistant subjects

“…We have recently reported on the effects of weight reduction on insulin sensitivity and sympathetic nerve activity. 10 We now report the effect of incubating plasmas from these subjects with cholesterol-loaded activated macrophages (THP-1 cells) related to the arterial insulin concentration, to whole-body insulin sensitivity derived from an oral glucose tolerance test (OGTT) and to CETP mass.…”